If you are thinking of looking out for a long lost friend or to know about someone's activity without their knowledge through a private investigator or simply a private, then there are certain things that you will have to take care of.
If using a private is your quest, here is the answer for it! First and foremost thing that you will have to do is to gather as much as initial information as possible.
To find the unknown address or activity, a private must be fed in with thorough background inputs.
Find all the pieces of any written or printed information you have about that person and hand them over to the private.
The more you give, the more you will get.
Even if you think that the particular piece of information is irrelevant, it is better to hand it over to the PI for he might find clues in it that you can never find.
Write down the names and addresses or phone numbers of all the common friends and also make separate lists for relatives and close friends.
Try providing detailed addresses for the close friends and relatives.
Collect envelopes and help your PI establish an address trial.
It will be useful to know about the person in question through his old neighbours and elicit the character sketch of the person in many perspectives.
The person might also have aliases which we don't know of.
Making a list of the favourite restaurants, hotels, hangouts, hobbies and interests of the person would help your PI get through many places and link each other to ultimately guess where that particular person would be and what he might be doing at that point of time.
There is no time to waste! Make your lists and rush to a PI now.